Spring-loaded ejectors for wood strand molding

ABSTRACT

Mold apparatus and method of production and ejection of molded wood strand three-dimensionally curved articles of manufacture, molded from a loosely felted flake mat, using an ejector pin assembly within said mold apparatus having ejector pins with pin head diameters of at least about 0.750 inches or greater, that exert a loaded ejector pin pressure of from approximately about 100 psi to about 1000 psi, to eject the molded wood strand article from the mold apparatus without causing excessive indentation and densification within the mat during mold processing.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention relates to the revolutionary wood flake moldingtechnology invented by wood scientists at Michigan TechnologicalUniversity during the latter part of the 1970s.

B. Background of the Art

Wood flake molding, also referred to as wood strand molding, is atechnique for molding three-dimensionally configured objects out ofbinder coated wood flakes having an average length of about 1¼ to about6 inches, preferably about 2 to about 3 inches; an average thickness ofabout 0.005 to about 0.075 inches, preferably about 0.015 to about 0.030inches; and an average width of 3 inches or less, most typically 0.25 to1.0 inches, and never greater than the average length of the flakes.These flakes are sometimes referred to in the art as “wood strands.”This technology is not to be confused with oriented strand boardtechnology (see e.g., U.S. Pat. No. 3,164,511 to Elmendorf) whereinbinder coated flakes or strands of wood are pressed into planar objects.In wood flake or wood strand molding, the flakes are molded intothree-dimensional, i.e., non-planar, configurations.

In wood flake molding, flakes of wood having the dimensions outlinedabove are coated with MDI or similar binder and deposited onto a metaltray having one open side, in a loosely felted mat, to a thickness eightor nine times the desired thickness of the final part. The looselyfelted wood flake mat is then covered with another metal tray, and thecovered metal tray is used to carry the mat to a mold. (The terms “mold”and “die”, as well as “mold die”, are sometimes used interchangeablyherein, reflecting the fact that “dies” are usually associated withstamping, and “molds” are associated with plastic molding, and moldingof wood strands does not fit into either category.) The top metal trayis removed, and the bottom metal tray is then slid out from underneaththe mat, to leave the loosely felted wood flake mat in position on thebottom half of the mold. The top half of the mold is then used to pressthe mat into the bottom half of the mold at a pressure of approximatelyabout 600 psi, and at an elevated temperature, to “set” (polymerize) theMDI binder, and to compress and adhere the compressed wood flakes into afinal three-dimensional molded part. The excess perimeter of the looselyfelted wood flake mat, that is, the portion extending beyond the moldcavity perimeter, is pinched off where the part defining the perimeterof the upper mold engages the part defining perimeter of the lower moldcavity. This is sometimes referred to as the pinch trim edge.

U.S. Pat. No. 4,440,708 and U.S. Pat. No. 4,469,216 disclose thistechnology. The drawings in U.S. Pat. No. 4,469,216 best illustrate themanner in which the wood flakes are deposited to form a loosely feltedmat, though the metal trays are not shown. By loosely felted, it ismeant that the wood flakes are simply lying one on top of the other inoverlapping and interleaving fashion, without being bound together inany way. The binder coating is quite dry to the touch, such that thereis no stickiness or adherence, which hold them together in the looselyfelted mat. The drawings of U.S. Pat. No. 4,440,708 best illustrate themanner in which a loosely felted wood flake mat is compressed by themold halves into a three-dimensionally configured article (see FIGS.2-7, for example).

This is a very unusual molding process as compared to a molding processone typically thinks of, in which some type of molten, semi-molten orother liquid material flows into and around mold parts. Wood flakes arenot molten, are not contained in any type of molten or liquid carrier,and do not “flow” in any ordinary sense of the word. Hence, those ofordinary skill in the art do not equate wood flake or wood strandmolding with conventional molding techniques.

However, during the molding process, the molded wood part produced tendsto adhere to the upper or lower mold half after the part is formed andthe mold is opened. This adherence problem decreases the number ofmolded wood parts that can be produced during a production run of suchparts, and increases the overall cost and time of production leading toproduction inefficiency. Conventional hydraulic ejector pins, like thoseused in plastic ejection molding, could be used in connection with awood flake molding apparatus to eject the molded part from the upper andlower mold halves of the apparatus, but add significant cost to themold. Spring-loaded ejector pins, like those used within stamping dies,could also be used in connection with a wood flake molding apparatus toeject the molded parts. However, spring-loaded ejector pins poke holesinto the loosely-felted wood flake mat as it is compressed and curedbetween closing upper and lower mold halves of the molding apparatus.

SUMMARY OF THE INVENTION

In the present invention, it has been surprisingly discovered that byusing one or more spring-loaded ejector pins having a pin head diameterof at least about 0.750 inches or greater and a loaded ejector pinpressure of approximately about 100 psi to 1000 psi within a moldapparatus, one can successfully mold a loosely felted wood flake matinto a molded part without poking holes in the mat or part, minimize orprevent excessive indentation and densification within the molded partat the point of contact with the ejector pin, and automatically ejectthe molded part from the mold as it is opened.

These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of spaced upper and lower moldhalves made in accordance with a preferred embodiment of the presentinvention, with spring-loaded ejectors in place in the upper and lowermold halves of the mold apparatus, and a loosely felted mat of woodflakes in place on the lower mold half;

FIG. 2 is a vertical cross-sectional view of the mold apparatus of thepreferred embodiment of the present invention, but with the mold halvesclosed;

FIG. 3 is a vertical cross-sectional view of the mold apparatus of thepreferred embodiment of the present invention, but with the moldreopened and the part removed; and

FIG. 4 is an enlarged cross-sectional view of a spring loaded ejector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the preferred embodiment, at least one ejector pin assembly 10 ismounted in each of mold halves 21 and 22 of mold 20 (FIG. 1) such thatas mold 20 is closed, loosely felted wood flake mat 30 is compressed andcured between upper mold half 21 and lower mold half 22 while ejectorpin 11 of ejector pin assembly 10 is compressed against spring 15 (FIG.2). When mold 20 is then opened, spring 15 causes ejector pins 11 toeject molded part 30′ from mold 20 (FIG. 3).

Ejector pin assembly 10 comprises of ejector pin 11 which furthercomprises of ejector pin head 12 terminating at shoulder 13. Shank 14extends from head 12 into the coil of spring 15 (FIG. 4). Pin 11articulates inwardly against spring 15 when mold halves 21 and 22 ofmold 20 are closed and compressed against mat part 30 and articulatesoutwardly when the mold halves are opened. Spring 15 is housed withinhousing 16, which is seated and secured in a receiving cavity bored intomold half 21 or 22, to a depth such that the surface of housing 16 isflush with the adjacent interior surface of mold half 21 or 22. Spring15 bears against the mold half 21 or 22 at the bottom of the housingreceiving bore, and its other end, against shoulder 13 of pin 11.Inwardly projecting annular spring retaining lip 17, at the top ofhousing 16, engages shoulder 13 of pin 11 to prevent spring 15 fromforcing pin 11 out of housing 16.

During the molding process, as mold halves 21 and 22 are closed, ejectorpin 11 is compressed inwardly against spring 15 (FIG. 2) into housing 16until shank 14 compresses against and stops at the base of housing 16,which is seated within mold halves 21 and 22. The length of shank 14 ofejector pin 11 relative to spring housing 16 is such that shank 14 willbottom out against the base of spring housing 16 when the top of pinhead 12 is flush with the top surface of mold half 21 or 22.

An ejector pin access tunnel 23 extends from the exterior of mold half21 or 22, to the base of the bore which receives ejector pin housing 16.It is smaller in diameter than the shank 14, such that spring 15surrounds its opening into the bore, and spring 15 cannot escape throughtunnel 23. The access tunnel should be of smaller diameter than theshank so the shank bottoms out at the bottom of the housing bore, andacts as a “stop” to prevent excess compression of the pin. A tool can beinserted through access tunnel 23 to dislodge stuck ejector pins. Oilcan be injected to lubricate such pins via ejector pin access tunnel 23.

It has been surprisingly discovered that a pin head 12 diameter ofapproximately about 0.750 inches or greater, under a loaded ejector pinpressure of from approximately about 100 psi to about 1000 psi,preferably about equal to mold pressure or less, and most preferably atabout mold pressure, will successfully eject molded part 30′ withminimal or no indentation and densification of the molded part 30′, atthe point of contact between loosely felted wood flake mat 30 and pinhead 12. The term “loaded ejector pin pressure” means the pressureexerted at the surface of ejector pin head 12, via spring 15, when mold20 is closed.

Typical maximum mold pressures in wood strand molding ranges from about300 to 700 psi, with 600 psi being most preferred. Typically during themolding process then, the loosely felted wood flake mat 30 is initiallypressed at a maximum mold pressure of about 600 psi for a period oftime. Mold pressure is then decreased to about 200 psi or aboutone-third of the initial pressure for a time, and then pressure isdecreased to a nominal level while the part continues to cure under theheat of mold 20, before mold 20 is opened.

The loaded ejector pin pressure of the preferred embodiment can begreater than the maximum mold pressure, but about 1000 psi maximum ispreferred. The loaded ejector pin pressure of the preferred embodimentcan be less than the preferred 100 psi, but one does not get as muchejection force from ejector pin 11 once mold halves 21 and 22 of mold 20are opened to eject molded part 30′. By utilizing a loaded ejector pinpressure at about mold pressure, one achieves minimal or no indentationand densification at the point of contact between loosely felted woodflake mat 30 and pin head 12 during the molding process, but maximumejection force from ejector pin 11 once mold halves 21 and 22 of mold 20are opened to eject molded part 30′ from the mold.

For example, ejector springs rated at about 1712 pounds per inch ofdeflection have about a 0.313-inch deflection or about 536 pounds ofresistance when compressed during the molding process utilizing thepreferred embodiment. The ejector pins 11 have a pin head 12 diameter ofabout 0.865 inch (0.5876 square inch) to exert a loaded ejector pinpressure of about 912 psi upon loosely felted wood flake mat 30 duringmold processing, while the mold pressure is about 600 psi.

If one increases the spring rating, the pin head diameter should beincreased to compensate for undesirable loaded ejector pin pressureswhich might indent or over densify the loosely felted wood flake matwhen transformed into the mold part beyond suitable parameters. Longerstroke springs and ejectors are desirable when die thickness allows fora longer ejector assembly.

To produce molded wood strand products, binder coated felted wood flakemat 30 is first placed between upper mold halves 21 and 22 of mold 20,overlying the cavity of lower mold half 21 (FIG. 1). Before compressingand curing, ejector pin assembly 10 is in its original position withinmold halves 21 and 22, such that ejector pin 11 is not depressed againstspring 15 within housing 16, pin head 12 is not flush with the surfacesof mold halves 21 and 22, and shank 14 is not stopped against the moldat the base of housing 16.

Then, both mold halves 21 and 22 of mold 20 are closed to apply heat andpressure to compress and cure felted wood flake mat 30 (FIG. 2). Duringthis compressing and curing step, ejector pin 11 of ejector pin assembly10 in each of mold halves 21 and 22 is compressed inwardly againstspring 15 within housing 16 until pin head 12 is flush with the surfaceof mold halves 21 and 22 of mold 20, and shank 14 is stopped against thebase of housing 16 to prevent indentation and densification of feltedwood flake mat 30 at its point of contact with pin head 12.

Following the compressing and curing step, mold halves 21 and 22 of mold20 are opened to reveal felted wood flake mat 30 which has beentransformed into molded part 30′ (FIG. 3). Molded part 30′ once formed,is ejected from the opened mold 20 via ejector pin 11 of ejectorassembly 10 when spring 15 outwardly forces shank 14 from housing 16until shoulder 13 is flush and stopped against inwardly projectingspring retaining lip 17. In this manner, pin head 12 returns to itsoriginal position which is not flush with the surface of mold halves 21and 22 to eject molded part 30′ from mold 20 to complete the moldingprocess (FIG. 3).

The wood flakes used can be prepared from various species of suitablehardwoods and softwoods used in the manufacture of particleboard.Representative examples of suitable woods include aspen, maple, oak,elm, balsam fir, pine, cedar, spruce, locust, beech, birch and mixturesthereof. Aspen is preferred.

Suitable wood flakes can be prepared by various conventional techniques.Pulpwood grade logs, or so-called round wood, are converted into flakesin one operation with a conventional roundwood flaker. Logging residueor the total tree is first cut into fingerlings in the order of 2-6inches long with a conventional device, such as the helical comminutingshear disclosed in U.S. Pat. No. 4,053,004, and the fingerlings areflaked in a conventional ring-type flaker.

Roundwood flakes generally are higher quality and produce stronger partsbecause the lengths and thickness can be more accurately controlled.Also, roundwood flakes tend to be somewhat flatter, which facilitatesmore efficient blending and the logs can be debarked prior to flakingwhich reduces the amount of less desirable fines produced during flakingand handling. Acceptable flakes can be prepared by ring flakingfingerlings and this technique is more readily adaptable to accept woodin poorer form, thereby permitting more complete utilization of certaintypes of residue and surplus woods.

Irrespective of the particular technique employed for preparing theflakes, the size distribution of the flakes is quite important,particularly the length and thickness. The wood flakes should have anaverage length of about 1¼ inch to about 6 inches and an averagethickness of about 0.005 to about 0.075 inches. The average length ofthe wood flakes is preferably about 2 to about 3 inches. In any givenbatch, some of the flakes can be shorter than 1¼ inch, and some can belonger than 6 inches, so long as the overall average length is withinthe above range. The same is true for the thickness.

The presence of major quantities of flakes having a length shorter thanabout 1¼ inch tends to cause the mat to pull apart during the moldingstep. The presence of some fines in the mat produces a smoother surfaceand, thus, may be desirable for some applications so long as themajority of the wood flakes, preferably at least 75%, is longer than 1⅛inch and the overall average length is at least 1¼ inch.

Substantial quantities of flakes having a thickness of less than about0.005 inches should be avoided, because excessive amounts of binder arerequired to obtain adequate bonding. On the other hand, flakes having athickness greater than about 0.075 inch are relatively stiff and tend tooverlie each other at some incline when formed into the mat.Consequently, excessively high mold pressures are required to compressthe flakes into the desired intimate contact with each other. For flakeshaving a thickness falling within the above range, thinner ones producea smoother surface while thick ones require less binder. These twofactors are balanced against each other for selecting the best averagethickness for any particular application. The average thickness of theflakes preferably is about 0.015 to about 0.25 inches, and morepreferably about 0.0020 inch.

The width of the flakes is less important. The flakes should be wideenough to ensure that they lie substantially flat when felted during matformation. The average width generally should be about 3 inches or lessand no greater than the average length. For best results, the majorityof the flakes should have a width of about {fraction (1/16)}-inch toabout 3 inches, and preferably 0.25 to 1.0 inches.

The blade setting on the flaker can primarily control the thickness ofthe flakes. The length and width of the flakes are also controlled to alarge degree by the flaking operation. For example, when the flakes arebeing prepared by ring flaking fingerlings, the length of thefingerlings generally sets the maximum lengths. Other factors, such asthe moisture content of the wood and the amount of bark on the woodaffect the amount of fines produced during flaking. Dry wood is morebrittle and tends to produce more fines. Bark has a tendency to morereadily break down into fines during flaking and subsequent handlingthan wood.

While the flake size can be controlled to a large degree during theflaking operation as described above, it usually is necessary to usesome sort of classification in order to remove undesired particles, bothundersized and oversized, and thereby ensure the average length,thickness and width of the flakes are within the desired ranges. Whenroundwood flaking is used, both screen and air classification usuallyare required to adequately remove both the undersize and oversizeparticles, whereas fingerling flakes usually can be properly sized withonly screen classification.

Flakes from some green wood can contain up to 90% moisture. The moisturecontent of the mat must be substantially less for molding as discussedbelow. Also, wet flakes tend to stick together and complicateclassification and handling prior to blending. Accordingly, the flakesare preferably dried prior to classification in a conventional typedrier, such as a tunnel drier, to the moisture content desired for theblending step. The moisture content to which the flakes are driedusually is in the order of about 6-weight % or less, preferably about 2to about 5-weight %, based on the dry weight of the flakes. If desired,the flakes can be dried to a moisture content in the order of 10 to 25weight % prior to classification and then dried to the desired moisturecontent for blending after classification. This two-step drying mayreduce the overall energy requirements for drying flakes prepared fromgreen woods in a manner producing substantial quantities of particleswhich must be removed during classification and, thus, need not be asthoroughly dried.

To coat the wood flakes prior to being placed as a loosely felted woodflake mat 30 within the cavity of lower mold half 22 within mold 20 ofthe preferred embodiment, a known amount of the dried, classified flakesis introduced into a conventional blender, such as a paddle-type batchblender, wherein predetermined amounts of a resinous particle binder,and optionally a wax and other additives, is applied to the flakes asthey are tumbled or agitated in the blender. Suitable binders includethose used in the manufacture of particleboard and similar pressedfibrous products and, thus, are referred to herein as “resinous particleboard binders.” Representative examples of suitable binders includethermosetting resins such as phenolformaldehyde,resorcinol-formaldehyde, melamine-formaldehyde, urea-formaldehyde,urea-furfuryl and condensed furfuryl alcohol resins, and organicpolyisocyantes, either alone or combined with urea- ormelamine-formaldehyde resins.

Particularly suitable polyisocyanates are those containing at least twoactive isocyanate groups per molecule, including diphenylmethanediisocyanates, m- and p-phenylene diisocyanates, chlorophenylenediisocyanates, toluene di- and triisocyanates, triphenylmethenetriisocyanates, diphenylether-2,4,4′-triisoccyanate andpolyphenylpolyisocyanates, particularlydiphenylmethane-4,4′-diisocyanate. So-called MDI is particularlypreferred.

The amount of binder added to the flakes during the blending stepdepends primarily upon the specific binder used, size, moisture contentand type of the flakes, and the desired characteristics of the partbeing formed. Generally, the amount of binder added to the flakes isabout 2 to about 15-weight %, preferably about 4 to about 10-weight %,as solids based on the dry weight of the flakes. When a polyisocyanateis used alone or in combination with a urea-formaldehyde resin, theamounts can be more toward the lower ends of these ranges.

The binder can be admixed with the flakes in either dry or liquid form.To maximize coverage of the flakes, the binder preferably is applied byspraying droplets of the binder in liquid form onto the flakes as theyare being tumbled or agitated in the blender. When polyisocyantes areused, a conventional mold release agent preferably is applied to the dieor to the surface of the felted mat prior to pressing. To improve waterresistance of the part, a conventional liquid wax emulsion preferably isalso sprayed on the flakes during the blinding step. The amount of waxadded generally is about 0.5 to about 2 weight %, as solids based on thedry weight of the flakes. Other additives, such as at least one of thefollowing: a coloring agent, fire retardant, insecticide, fungicide,mixtures thereof and the like may also be added to the flakes during theblending step. The binder, wax and other additives, can be addedseparately in any sequence or in combined form.

The mixture of binder, wax and flakes or “furnish” from the blendingstep is formed into a loosely felted, layered wood flake mat 30, whichis placed within the cavity of lower mold half 22 prior to the moldingand curing of the mat into a molded wood particle product. The moisturecontent of the flakes should be controlled within certain limits so asto obtain adequate coating by the binder during the blending step and toenhance binder curing and deformation of the flakes during molding.

The presence of moisture in the flakes facilitates their bending to makeintimate contact with each other and enhances uniform heat transferthroughout the mat 30 during the molding step, thereby ensuring uniformcuring. However, excessive amounts of water tend to degrade somebinders, particularly urea-formaldehyde resins, and generate steam whichcan cause blisters. On the other hand, if the flakes are too dry, theytend to absorb excessive amounts of the binder, leaving an insufficientamount on the surface to obtain good bonding and the surfaces tend tocause hardening which inhibits the desired chemical reaction between thebinder and cellulose in the wood. This latter condition is particularlytrue for polyisocyanate binders.

Generally, the moisture content of the furnish after completion ofblending, including the original moisture content of the flakes and themoisture added during blending with the binder, wax and other additives,should be about 5 to about 25 weight %, preferably about 5 to about 7weight %. Generally, higher moisture contents within these ranges can beused for polyisocyanate binders because they do not produce condensationproducts upon reacting with cellulose in the wood.

The furnish is formed into a generally flat, loosely felted, mat,preferably as multiple layers. A conventional dispensing system, similarto those disclosed in U.S. Pat. Nos. 3,391,223 and 3,824,058, and4,469,216 can be used to form the mat. Generally, such a dispensingsystem includes trays, each having one open side, carried on an endlessbelt or conveyor and one or more (e.g., 3) hoppers spaced above andalong the belt in the direction of travel for receiving the furnish.

When a multi-layered mat is formed in accordance with a preferredembodiment, a plurality of hoppers usually are used with each having adispensing or forming head extending across the width of the formingbelt for successively depositing a separate layer of the furnish as thetray is moved beneath the forming heads. Following this, the tray istaken to mold 20 to place the loosely felted mat 30 within the cavity oflower mold half 22, by sliding the tray out from under mat 30.

In order to produce molded wood strand products having the desired edgedensity characteristics without excessive blistering and springback, theloosely felted mat 30 should preferably have a substantially uniformthickness and the flakes should lie substantially flat in a horizontalplane parallel to the surface of the forming belt and be randomlyoriented relative to each other in that plane. The uniformity of the matthickness can be controlled by depositing two or more layers of thefurnish on the forming belt and metering the flow of furnish from theforming heads.

Spacing the forming heads above the forming belt so the flakes must dropabout 1 to about 3 feet from the heads en route to the carriage canenhance the desired random orientation of the flakes. As the flat flakesfall from that height, they tend to spiral downwardly and land generallyflat in a random pattern. Wider flakes within the range discussed aboveenhance this action. A scalper or similar device spaced above theforming belt can be used to ensure uniform thickness or depth of themat, however, such means usually tend to align the top layer of flakes,i.e., eliminate the desired random orientation. Accordingly, thethickness of the mat preferably is controlled by closely metering theflow of furnish from the forming heads.

The mat thickness used will vary depending upon such factors as the sizeand shape of the wood flakes, the particular technique used for formingthe mat, the desired thickness and density of the mold wood productproduced, the configuration of the molded wood product, and the moldingpressure to be used. In addition, after the molded wood strand part isproduced by the method of the present invention, any flashing and anyplugs are removed by conventional means, and the peripheral edges of themolded part can be trimmed to the desired final dimensions. Thepreferred embodiment of the present invention can include means, whichprovide built-in trimming and removal of plugs and flashing duringprocessing as well.

Molding temperatures, pressures and times vary widely depending upon thethickness and desired density of the molded wood strand part 30′, sizeand type of wood flakes, moisture content of the flakes, and the type ofbinder used. The molding temperature used is sufficient to at leastpartially cure the binder and expel water from the loosely felted woodflake mat 30 within a reasonable time period and without charring thewood. Generally, a molding temperature ranging from ambient up to about450° F. can be used. Temperatures above about 450° F. can cause charringof the wood. When a binder system including, a urea-formaldehyde resinand a polyisocyanate is used, a molding temperature of about 250° toabout 375° F. is preferred, while a molding temperature of about 300° toabout 425° F. is preferred for phenol-formaldehyde resin binders.

The molding pressure used should be sufficient to press the wood flakesinto intimate contact with each other without crushing them to the pointwhere lignin starts to exude, causing a breakdown in the fibers with aresultant degradation in structural integrity. The maximum moldingpressure on the net die/mold area typically is about 300 to 700 psi.

The time of the molding or press cycle is sufficient to at leastpartially cure the binder to a point where the molded wood part hasadequate structural integrity for handling. The press cycle typically isabout 2 to about 10 minutes; however, shorter or longer times can beused when pressure-curing binders are employed when more complete curingof certain thermosetting binders is desired.

The mold apparatus having spring-loaded ejector assemblies of thepreferred embodiment and method of ejecting molded wood parts producedusing such an embodiment solve problems of producing such parts, whichwere not solved by the prior art. The preferred embodiment and method ofproduction using the preferred embodiment solve the problem of moldedwood parts sticking to the mold apparatus, increase efficiency of moldedwood part production, and allow for production of molded wood parts inan assembly-line like fashion without having to remove each molded partby hand or other non-automated means when produced.

In addition, the preferred embodiment and method of production utilizingthe preferred embodiment allow for the surprising discovery that moldedwood parts can be ejected from mold apparatuses without poking holes inthe loosely felted wood flake mat, without causing excessive indentationand densification of the mat at the point of contact with the pin head,and at a low cost, by using spring-loaded ejector assemblies having apin head diameter of at least about 0.750 inches or greater.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The above description, however, is that of thepreferred embodiments only. Modifications of the invention will occur tothose skilled in the art and to those who make or use the invention.Therefore, it is understood that the embodiment described above ismerely for illustrative purposes and not intended to limit the scope ofthe invention, which is defined by the following claims as interpretedaccording to the principles of patent law, including the Doctrine ofEquivalents.

The invention claimed is:
 1. An apparatus for ejecting a molded woodpart from a mold apparatus comprising: a lower mold half and an uppermold half, each having a surface configured to define a cavitytherebetween; at least one ejector pin assembly in at least one of saidmold halves wherein said ejector assembly further comprises: a housinghaving an inwardly projecting retainer lip, which surrounds an ejectorpin opening; an ejector pin positioned in said housing, and having a pinhead projecting through said housing opening and terminating at anoutwardly projecting shoulder, from which extends a narrower shank,wherein the diameter of said pin head is at least about 0.750 inches orgreater; a spring contained within said housing and bearing against saidshoulder of said ejector pin, said ejector pin shank extending into saidhousing; said ejector pin shoulder bearing against said retainer lipunder pressure of said spring; said spring compressing inwardly andexpanding outwardly allowing said ejector pin to articulate inwardly andoutwardly when compressed and decompressed by said mold halves; and saidspring being selected so as to exert a loaded ejector pin pressure, atthe surface of said pin head, of from approximately about 100 psi to1000 psi when said mold upper and lower mold halves are closed on a partlocated in the closed mold.
 2. The apparatus of claim 1, wherein saidpin head diameter is 0.865 inch.
 3. The apparatus of claim 1, whereinsaid loaded ejector pin pressure is 600 psi.
 4. The apparatus of claim1, wherein said loaded ejector pin pressure is about equal to or lessthan mold pressure exerted by said mold halves of said mold.
 5. Theapparatus of claim 1, wherein said loaded ejector pin pressure isapproximately equal to a mold pressure exerted by said mold halves ofsaid mold.
 6. A method of ejecting a molded three dimensionally curvedarticle formed from binder coated wood flakes from a mold apparatuscomprising: forming a loosely felted mat of said wood flakes; depositingsaid mat onto a lower mold half of said mold apparatus; compressing andheating said mat between an upper mold half and said lower mold half,said mold halves forming a part defining mold cavity therebetween toform a molded wood part; and ejecting said molded part via at least oneejector pin assembly in at least one of said mold halves wherein saidejector assembly further comprises: a housing having an inwardlyprojecting retainer lip, which surrounds an ejector pin opening; anejector pin positioned in said housing, and having a pin head projectingthrough said housing opening and terminating at an outwardly projectingshoulder, from which extends a narrower shank, wherein the diameter ofsaid pin head is at least about 0.750 inches or greater; a springcontained within said housing and bearing against said shoulder of saidejector pin, said ejector pin shank extending into said housing; saidejector pin shoulder bearing against said retainer lip under pressure ofsaid spring; said spring compressing inwardly and outwardly allowingsaid ejector pin to articulate inwardly and expanding outwardly whencompressed and decompressed by said mold halves; and said spring beingselected so as to exert a loaded ejector pin pressure, at the surface ofsaid pin head, of from approximately about 100 psi to 1000 psi when saidmold upper and lower mold halves are closed on said loosely felted mat.7. The method of claim 6, wherein said wood flakes have an averagelength of from about 1¼ to about 6 inches, an average thickness of fromabout 0.015 to about 0.25 inches, and an average width of less than theaverage length, and no greater than about 3 inches.
 8. The method ofclaim 7, wherein said wood flakes of said mat have an average length offrom about 2 to about 6 inches.
 9. The method of claim 7, wherein saidwood flakes of said mat have an average thickness of from about 0.015 toabout 0.030 inches.
 10. The method of claim 7, wherein said wood flakesof said mat have an average width of from about 0.25 to about 1.0inches.
 11. The method of claim 7, wherein said pin head diameter is0.865 inch.
 12. The method of claim 7, wherein said loaded ejector pinpressure is 600 psi.
 13. The method of claim 7, wherein said loadedejector pin pressure is about equal to or less than mold pressureexerted by said mold halves of said mold.
 14. The method of claim 7,wherein said loaded ejector pin pressure is approximately equal to moldpressure exerted by said mold halves of said mold.